Many people have asked what pests like tomato plants... here is a small list of what pest may be bothering you tomato plant.
1. Colorado potato beetle I find these eary spring.
2. Missing leaves might suggest a hornworm.
3. Blister Beetles these use come out about mid-summer.
4. Fruit Flies This is after fruit begins to ripen.
5. Slugs I have these when my fruit is on the ground and there are a few overly-ripen close together.
I have found the easiest method to get rid of the Colorado Potato Beetle and the Tomato Horn Worm is to get out early and pick them off...starting the beginning of the season....before they take over your garden.
I pick them and place them in a bucket with 1 quart of water and 1 teaspoon liquid soap. This way they won't crawl back up the bucket and get out and it is safe to throw the remains in my compost pile.
I have many recipes that you can use to spray them but if you want immediate results you can always hand pick.